Trolleys which transport loads or workpieces in manufacturing plants and which travel on the lower flange of a beam are disclosed in Federal Republic of Germany Patent document OS 36 27 358. The trolleys therein disclosed are suspension trolleys for crane systems which lift a workpiece and transport it suspended to a work station. Thereafter, the workpiece is lifted again and deposited at another work station. Since this procedure is not always optimal for assembly line manufacture, roller tables are frequently more suitable because their width can be selected to correspond to that of the workpiece being transported.